1. Field of the Invention
The present invention relates to a phase-change optical information recording medium which includes a recording layer located on a substrate and in which information can be recorded and erased. In particular, the present invention relates to a phase-change optical information recording medium in which information can be recorded and erased utilizing reversible phase-change of the recording layer between an amorphous phase and a crystal phase. In addition, the present invention also relates to an information recording and reading method using the phase-change optical information recording medium.
2. Description of the Related Art
Japanese Laid-Open Patent Publication No. 8-124218 discloses a phase-change optical information recording medium in which information can be recorded and erased utilizing mark edge recording. The disclosed optical recording medium is prepared by forming a first dielectric layer, a recording layer, a second dielectric layer, a reflecting layer, a third dielectric layer, and a UV curable resin layer on a substrate in this order. The reflecting layer is formed of a transparent ultra-thin film of a metal, Si, or Ge. The third dielectric layer is formed of a dielectric material having a refractive index n more than 1.5. The medium satisfies the following relationship:Ac>Aawherein Ac represents the absorptance in a crystalline state and Aa represents the absorptance in an amorphous state.
In this known art, an optical information recording medium having a crystalline absorptance Ac larger than the amorphous absorptance Aa (that is, the recording medium having a crystalline reflectance smaller than the amorphous reflectance) is provided. However, the recording medium has a drawback in that the medium does not have compatibility with CD-ROMs in view of reflectance.
Japanese Laid-Open Patent Publication No. 11-39716 discloses a medium having such a large refractive index as 2.2 to 2.3; however, the reflectance and characteristics of the medium having such a large refractive index widely change because the variation of the film thickness seriously influences on the characteristics.